HDU-2874-森林求LCA/tarjan

http://acm.hdu.edu.cn/showproblem.php?pid=2874

给出一个森林，询问任意两点最短距离。

tarjan跑一遍即可，就是这个题卡内存，vector会MLE，换前向星就好了。

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<map>
 #include<set>
 #include<stack>
 #include<deque>
 #include<bitset>
 #include<unordered_map>
 #include<unordered_set>
 #include<queue>
 #include<cstdlib>
 #include<ctype.h>
 #include<ctime>
 #include<functional>
 #include<algorithm>
 #include<bits/stdc++.h>
 using namespace std;
 #define LL long long
 #define pii pair<int,int>
 #define mp make_pair
 #define pb push_back
 #define fi first
 #define se second
 #define inf 0x3f3f3f3f
 #define debug puts("debug")
 #define mid ((L+R)>>1)
 #define lc (id<<1)
 #define rc (id<<1|1)
 const int maxn=;
 const int maxm=;
 const double PI=acos(-1.0);
 const double eps=1e-;
 const LL mod=1e9+;
 LL gcd(LL a,LL b){return b==?a:gcd(b,a%b);}
 LL lcm(LL a,LL b){return a/gcd(a,b)*b;}
 LL qpow(LL a,LL b,LL c){LL r=; for(;b;b>>=,a=a*a%c)if(b&)r=r*a%c;return r;}
 template<class T>
 void prt(T v){for(auto x:v)cout<<x<<' ';cout<<endl;}
 struct Edge{int v,w,next;}e,e1[],e2[];
 int first1[maxn],first2[maxn],tot1,tot2;
 void add1(int u,int v,int w){
     e1[tot1].v=v;
     e1[tot1].w=w;
     e1[tot1].next=first1[u];
     first1[u]=tot1++;
 }
 void add2(int u,int v,int w){
     e2[tot2].v=v;
     e2[tot2].w=w;
     e2[tot2].next=first2[u];
     first2[u]=tot2++;
 }

 bool vis[maxn];
 int f[maxn],d[maxn],ans[];
 int getf(int u){return f[u]==u?u:f[u]=getf(f[u]);}
 void tarjan(int u){
     vis[u]=;
     for(int i=first1[u];~i;i=e1[i].next){
         e=e1[i];
         int v=e.v,w=e.w;
         if(!vis[v]){
             d[v]=d[u]+w;
             tarjan(v);
             f[v]=u;
         }
     }
     for(int i=first2[u];~i;i=e2[i].next){
         e=e2[i];
         int v=e.v,id=e.w;
         if(vis[v]){
             ans[id]=d[u]+d[v]-*d[getf(v)];
         }
     }
 }
 void read(int &n){
     n=; char c=getchar();
     while(c<''||c>'')c=getchar();
     while(c>=''&&c<='') n=(n<<)+(n<<)+c-'',c=getchar();
 }
 int main(){
     int t,n,m,i,j,u,v,w;
     while(~scanf("%d%d%d",&n,&m,&t)){
         for(i=;i<=n;++i)f[i]=i;
         tot1=tot2=;
         memset(first1,-,sizeof(first1));
         memset(first2,-,sizeof(first2));
         while(m--){
             //scanf("%d%d%d",&u,&v,&w);
             read(u),read(v),read(w);
             add1(u,v,w);
             add1(v,u,w);
         }
         for(i=;i<=t;++i){
             ans[i]=-;
             //scanf("%d%d",&u,&v);
             read(u),read(v);
             add2(u,v,i);
             add2(v,u,i);
         }
         memset(d,-,sizeof(d));
         for(i=;i<=n;++i){
             if(d[i]==-) d[i]=,memset(vis,,sizeof(vis)),tarjan(i);
         }
         for(i=;i<=t;++i){
             if(ans[i]==-) puts("Not connected");
             else printf("%d\n",ans[i]);
         }
     }
     return ;
 }